What Is the Difference Between Hamiltonian and Hermitian Operators?

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Discussion Overview

The discussion revolves around the distinction between Hamiltonian and Hermitian operators, focusing on their definitions, properties, and implications in quantum mechanics and mathematics. Participants explore the mathematical and physical contexts of these terms.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that "Hermitian" refers to a broad class of operators with a specific mathematical property, while "Hamiltonian" is a particular operator in quantum mechanics related to system dynamics.
  • It is noted that while a Hamiltonian must be Hermitian, not all Hermitian operators qualify as Hamiltonians.
  • One participant points out that "Hamiltonian" can also function as an adjective related to Hamilton.
  • There is a suggestion that the term "Hermitian" may be misleading, advocating for the use of "symmetric" and "self-adjoint" in quantum physics discussions.
  • Another participant agrees that "self-adjoint" is preferable in the context of infinite-dimensional spaces, while acknowledging that "Hermitian" is adequate in finite spaces.
  • It is mentioned that the concept of the Hamiltonian has roots in Classical Mechanics and is not exclusive to quantum mechanics.

Areas of Agreement / Disagreement

Participants express differing views on the terminology and appropriateness of using "Hermitian" versus "self-adjoint," indicating a lack of consensus on the best terminology for various contexts.

Contextual Notes

The discussion highlights potential limitations in the definitions and contexts of Hermitian and Hamiltonian operators, particularly regarding their applicability in finite versus infinite-dimensional spaces.

piareround
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If anyone has time could they please answer this question.


I was looking and concept of the the http://en.wikipedia.org/wiki/Hamiltonian_(quantum_mechanics)" , I was wonder is their a difference between the two terms? If so how are Hermitian and the Hamiltonian different? Can anyone give an example?
 
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"hermitian" is a general mathematical property which apples to a huge class of operators, whereas a "Hamiltonian" is a specific operator in quantum mechanics encoding the dynamics (time evolution, energy spectrum) of a qm system.

The difference should be clear.

A Hamiltonian must be hermitian, whereas not every hermitian operator is a Hamiltonian.

(the number 17 is positive number, but not every positive number is equal to 17 :-)
 
'Hamiltonian' is also an adjective :-) (pertaining to Hamilton ?)

On a serious note, 'hermitean' is misleading. In the mathematics of quantum physics we should use <symmetric> and <self-adjoint>.
 
Last edited:
bigubau said:
... 'hermitean' is misleading. In ... quantum physics we should use <symmetric> and <self-adjoint>.
I fully agree!
 
In finite spaces Hermitian works fine, but I agree that for infinite dimensional spaces self-adjoint is the better term.
 
Also, the Hamiltonian is a concept that extends from Classical Mechanics. It is not unique to quantum mechanics
 

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